1
2251-600X
Isfahan University of Technology
82
General
Flow Visualization by Conditional Sampling of a Single X-Wire Probe in a Very Long Run Experiment
Mojtaba Rajaee
1
1
1996
14
2
1
11
25
10
2014
Flow visualization techniques using tracer markers such as die, smoke, hydrogen bubbles, etc., have been widely used in experimental investigations of large scale structures of a variety of flow fields. They have played an important role in understanding the physics of the coherent structures' formation and evolution in the transitional as well as the turbulent regions of the flow fields. However, they lack to provide detailed quantitative information about the flow. Here, a new approach is taken in obtaining quantitative flow field snapshots from a region of a two-dimensional free shear flow mixing layer. A single cross-wire probe is used to make measurements of the flow in a time frame phase locked with the coherent flow structures which facilitates reconstructed flow snapshots from the hot-wire measurements in a very long run experiment. A new detailed calibration updating scheme is developed to resolve the problem of calibration validity encountering very long time hot-wire measurements. This is a key factor in facilitating reconstructed flow snapshots that satisfy the continuity equation with a very high accuracy.
80
General
Using Pseudo-Inverse to Eliminate the Limitation of the Number of Colors in Colorimetric Match
S. H. Amirshahi
1
1
1996
14
2
13
20
25
10
2014
An algorithm is suggested for implementation of unlimited primaries in two-constants Kubelka-Munk color matching attempt. Allen's method for tristimulus color matching which was limited to four colorants in two constant theory, dealt with inversable matrices. By application of the pseudo-inverse, it is not necessary to limit the number of primary colors to four as Allen suggested. The suggested method is programmed to a color matching attempt with five pre-colored fibers.
81
General
Simulation of Dispersion of Polluted Gases in Atmosphere
V. Kalantar and M. Abbaspour
1
1
1996
14
2
21
41
25
10
2014
A computer program was developed to predict the dispersion of gas pollutant in the atmosphere. This program relies on puff method, and in order to consider the wind shear effects, the program has the ability to consider the complete dynamic and unsteady atmospheric conditions. Plume rise of hot pollutants due to buoyancy effects was also considered. The program has the capacity to perform the realtime calculations and uses on-line data of atmospheric conditions that are measured by an anemometer and a thermometer. In order to consider the effects of presence of building and other obstacles or sudden change in surface roughness on dispersion of released materials, a model was added to evaluate the dispersion coefficients in the wake of obstacles. Using this relatively complete simulation, we analyzed the effects of above parameters on the dispersion of gas pollutants in atmosphere and the interpretation of the results is presented.
83
General
A Novel Algorithm for Digital Distance Relaying
F.Ghassemi and R.safari
1
1
1996
14
2
43
59
25
10
2014
Distance relays are used to protect EHV and HV Transmission lines. Over the past decades many algorithms have emerged for digital distance relays. These are based on the calculation of the transmission line impedance from the relaying to fault points. In this paper a novel method for digital distance relaying is proposed. In the method the tracking procedure is implemented. The method uses the calculus of variations for optimization of functionals. The method tracks the fundamental component of the waveforms and at the same time calculates the fault loop impedance. This eliminates the need for a pre-algorithm filtering which in turn improves the speed of the relay. Comparison with other algorithms has shown that the proposed method has a faster response and improved accuracy, in particular when a long line is considered.
84
General
Hydrodynamic Analysis of Marine Buoys
A. R. zamani and M. S. Saidi
1
1
1996
14
2
61
72
25
10
2014
In dynamic analysis of floating structures, the designer needs to know the wave forces due to incident and scattered waves on the structure. In this work, the flow field around the body is solved based on the potential theory with considering the free surface and sea bed effects. Using this theory, the wave forces exerted on two typical sea buoys with spherical and disc-type bodies are determined. Comparison of these results with the one obtained using Haskind method shows good accuracy of the present method.
85
General
Earthquake Analysis of 3-D Structures on Sliding Foundation Using Yield Equation of the Contact Surface
M. M. Saadatpour and N. A. Falah
1
1
1996
14
2
73
82
25
10
2014
A solution technique for the dynamic analysis of asymmetric base-isolated buildings, subject to earthquake ground motion, is presented. To develop the formulation, a yield surface as a function of both shear force and torsion moment of the sliding surface with rigid perfectly plastic behavior is constituted. To achieve the objective, the yield stress is defined by the friction coefficient through a simple relation. Having introduced the mathematical model of the yield surface, the simple conditions of being at the onset of sliding and nonsliding phases of motion are given. Based on the elaborated model, the earthquake dynamic analysis of a 3-D structure is performed. The results are in good agreement with those obtained by the finite-element modeling of the surface.